[unreadable] Many phenotypes are encoded in the genome of an organism, and the first step in the expression of these phenotypes is the transcription of a gene into RNA. Essentially, the phenotype of the organism is shaped by the transcription of specific genes in specific cell types, at specific points in development, and in a specific sex. Coupling gene expression with genome sequences from multiple species allows for a high resolution examination of the evolutionary dynamics of the regulation of transcription. High quality gene expression data will be collected from three somatic tissues and the gonads of males and females of four species of Drosophila to test hypotheses regarding the evolution of gene expression. These data will be used to determine the plasticity or conservation of gene expression for individual genes. Additionally, the expression profiles of duplicated genes will be examined to determine how gene expression is partitioned following duplication and how often duplicated genes obtain new functions. Finally, comparisons will be made between genes on X chromosomes and those on autosomes to determine what causes the differences in sex-bias between these two classes of chromosomes. Relevance: While many genetic diseases are caused by mutations that disrupt the proper functioning of a gene product, many others are caused by a gene not being expressed properly. The proposed research will address a few of the major factors responsible for determining how genes are expressed using the Drosophila model system. These factors will be analyzed on a genome-wide scale to study how the genomic context in which a gene is found affects how that gene is expressed throughout the organism. [unreadable] [unreadable] [unreadable] [unreadable]